Explosive device



Feb. 13, 1962 R. J. MILLER 3,020,844

EXPLOSIVE DEVICE Filed Dec. 29, 1958 INVENTOR. ROSS J. MILLER 3,2,84tPatented Feb. 13, teen 3,020,844 EXPLOSIVE DEVICE Ross J. Miller,Pitman, N.J., assignor to E. I. du Pont de Nemours and Company,Wilmington, DeL, a corporation of Delaware Filed Dec. 29, 1958, Ser. No.783,454 Claims. (Cl. 102-27) The present invention relates to a novelblasting initiation assembly. More particularly, the present inventionrelates to a novel connecting assembly whereby a detonation impulse istransmitted from low-energy connecting cord to detonating fuse.

Often in blasting operations, the detonation impulse is transmitted tothe main explosive charges by means of detonating fuse which containsfrom 40 to 120 grains of high explosive per linear foot. Thistransmission is accomplished by a trunk line of fuse to which areattached branch lines of the same fuse leading down into the individualboreholes. Due to the high brisance produced by the exploding core ofthe described detonating fuse, these attachments may be madesatisfactorily by knot-ting the branch detonating fuse to the trunkline. However, the noise and destructive violence produced by theexplosion of such detonating fuse on the surface of the earth hasresulted in much dissatisfaction with its use as a trunk line. Theunpleasing noise level reached by an exploding length of conventionaldetonating fuse in air is very high. Many users of such fuse inpopulated areas have received complaints from individuals who have beendiscomforted by the noise produced. In many instances in rural areas,complaints that blast noise has had an adverse effect upon livestockhave resulted in suspension of operations and law suits. Due to thepsychological nature of these complaints, they are much more difficultto deal with than are complaints arising from actual damage. A further,and more restrictive, disadvantage of such detonating fuse trunk linesis that they cannot be used in operations where the line of initiationmust pass objects which will not withstand a shattering explosive force.Expensive, elaborate, and time-consuming shielding methods such as, forexample, covering the entire length of the trunk line with earth, mustbe employed in order to circumvent these undesirable effects.

Under many circumstances, the use of a more recently developed device,low-energy connecting cord, instead of detonating fuse, as the trunkline has been found to be advantageous. This connecting cord, describedin detail in copending application Serial No. 744,586 filed June 25,1958, now Patent Number 2,982,210 by D. J. Andrew, R. W. Felch, and G.A. Noddin, comprises a continuous core of 0.1 to 2 grains of acap-sensitive high explosive per foot of length confined within a metalsheath, which preferably is countered with a strengthening andprotective coating. The described cord is capable of propagatingdetonation at the velocity of conventional detonating fuse but withoutthe accompanying destructive shattering or annoying noise. However,owing to the reduced brisance, transmission of detonation from alow-energy connectingcord trunk line to a conventional detonating fusebranch line cannot be achieved by the methods ordinarily employed withdetonating fuse, i.e., knotting the ends or taping the lengthsside-by-side. Therefore, a need exists for a means of reliablytransmitting a detonation impulse from low-energy connecting cord to adetonating fuse branch line with an essentially simultaneouscontinuation of the detonation impulse in the trunkline.

Accordingly, an object of the present invention is to provide an easilypracticed means of initiation for cordlike explosive devices, such asdetonating fuse and the like. Another object of the present invention isto provide an assembly for connecting low-energy connecting cord anddetonating fuse in such a manner that the detonation impulse istransmitted reliably to the detonating fuse from the low-energyconnecting cord. A further object of the invention is the provision ofan efficient blasting method wherein no objectionable noise orabove-ground shattering is encountered. Other objects will becomeapparent as the invention is more fully described.

' We have found that the foregoing objects may be achieved when weprovide as a connector for low-energy connecting cord and detonatingfuse a blasting initiation assembly which comprises a tubular metalshell integrally closed at one end and containing a cap-sensitivedetonating explosive therein and concentrically disposed around at leasta portion'o-f said shell and contiguously joined therewith a cylindricalsleeve, the end portion of said sleeve opposite said shell having aninside diameter essentially 7 equal to the inside diameter of saidshell, and having in tion of detonating fuse of sufiicient lengththrough the apertures provided. Under circumstances where no tension isencountered, crimping of the sleeve may be omitted as the sleeve hasbeen provided with an extension the I inside diameter of which isessentially equal to the outside diameter of low-energy connecting cordand which can retain the cord firmly, particularly if alternate meansfor retaining the cord are provided in the surface of this portion ofthe sleeve. The cord should be crimped in the shell to insure initiationof the explosive charge in the shell and to provide a water-tightjunction.

In order to described more completely the nature of the presentinvention, reference is now made to the accompanying drawings, in whichthe same number has been used to indicate the equivalent parts of theassembly and FIGURE 1 is a top view of one embodiment of the assembly ofthe present invention,

' FIGURE 2 is a schematic View, partially in cross-section, of theassembly with a length of detonating fuse and two lengths of low-energyconnecting cord inserted,

FIGURE 3 is a top view, partially in cross section, of the assemblyprovided with an aperture which is pear shaped and a shell having adelay element interposed adjacent the explosive charge.

Referring to the drawings in more detail, and particularly FIGURE 1, 1is a metal shell having one integrally closed end and containingexplosive charges 9 and 10. 2 represents a cylindrical metal sleevehaving one end concentrically disposed around the closed end portion ofshell 1 and having a pair of apertures 3 which form an opening of atleast the diameter of detonating fuse and are located in sleeve 2 so asto be contiguous to the closed end of shell 1. 4 represents the otherend portion of sleeve 2 and has an inside diameter essentially equal tothe inside diameter of shell 1.

In FIGURE 2, l, 2, 3, and 4 are the same as in FIGURE 1. 5 and 7represent terminated lengths of low-energy connecting cord inserted intothe assembly, the terminal end of cord 7 being retained in the assemblyadjacent to the primer charge of a heat-sensitive priming explosive 9 bya circumferential crimp 8. 6 is a length of conventional detonating fuseinserted through the apertures 3. The primer charge 9 is initiable bycord 7 and is above the base charge of a detonating explosive 10 whichis disposed at the closed end of shell 1 and which initiates detonatingfuse 6. 16 represents the explosive core of the low-energy connectingcord 5. 17 is a metal sheath surrounding the core 25, and 18 is anonmetallic countering around sheath 17. The explosion of detonatingfuse 6 immediately initiates the adjacent low-energy connecting-cordtrunk line 5. Care must be taken so that the connecting cord isessentially abutted against the length of detonating fuse 6 and thatdetonating fuse 6 is adjacent the closed end of shell 1 in order toassure continuation of the detonation. Therefore, aperture 3 ispreferably somewhat wider than the diameter of ordinary detonating fusein order that a visual inspection may insure that the terminal portionof cord 5 is closely adjacent to detonating fuse 6, detonating fuse 6then being firmly maintained between the closed end of shell 1 and theend portion of cord 5 by being squeezed between these two.

In FIGURE 3, 1, 2, 3, 4, 9, and 10 are as in FIGURES 1 or 2. 11 areinwardly directed prongs provided as an aid in retaining the low-energyconnecting cord in the portion of smaller diameter 4 of sleeve 2. 12represents a circumferential crimp which joins shell 1 and sleeve 2integrally. 13 represents a delay element comprising anexothermic-burning mixture of boron and red lead in terposed adjacentthe primer charge 9. 14 represents an open-ended metal capsule having acentral aperture 15 interposed adjacent the delay element 13 and whichprovides static resistance.

In applying my invention to blasting operations, the low-energyconnecting-cord trunk line is severed and one cut end inserted into theopen end of the shell, and the shell is crimped. Then detonating fuse ofa suitable length is threaded through the apertures provided therefor,one end of the detonating fuse extending to the bottom of the borehole.Next, the other cut end of the low-energy connecting-cord trunk line isinserted into the end portion of the sleeve, firmly abutted against thedetonating fuse, and crimped. Optionally, inwardly directed prongs maybe provided in the Wall of the portion of the sleeve having a smallerdiameter in order to retain the low-energy connecting cord during thecrimping operation. The end of the detonating fuse not extending to thebottom of the borehole is buried in the stemming or is taped or tied tothe longer extension to insure against the withdrawal of the fuse fromthe assembly. The as-, sembly thus formed may be buried to eliminate theescape: of noise from the detonating fuse.

Low-energy connecting cord has a larger outside diameter than that ofdetonating fuse in order to insure against the use of the cord in anassembly or fitting designed for use only with the fuse or vice versa.In order to provide the maximum side wall and corresponding strength atthe portion of the sleeve containing the apertures, the apertures mustbe in that portion having the larger diameter.

The exemplified shell containing an explosive charge is necessary, dueto the low brisance produced by exploding low-energy connecting cord, inorder to initiate the detonating fuse. Within the shell are disposed atthe closed end a base charge of a cap-sensitive detonating highexplosiveof the type conventionally used as the base charge of initiators, i.e.,PETN, RDX, lead azide, picryl sulfone, etc., and adjacent the basecharge a primer charge of a high explosive which is readily initiated bythe low-energy connecting cord. Examples of such priming compositionsare lead azide, diazodinitrophenol, and mercury fulminate. If a timedelay is desired in the blasting operation in order to provide improvedand more predictable burden movement, as'is often the case, a delaycharge may be included adjacent to the primer charge as is shown inFIGURE 3. Such a delay device is described in copending applicationSerial No. 749,848 filed on July 21, 1958, by R. J. Miller and G. A.Noddin and assigned to the present assignee and contains as the delayelement a layer of a mixture 'of boron and red lead. The low-energyconnecting cord and the detonating fuse will have explosive corescomprising a cap sensitive high explosive, for example, PETN, RDX, leadazide, or picryl sulfone.

It is not necessary that the sleeve cover more than a portion of theshell. However, it may be extended as far as that portion of the shellwhich is to be crimped. Furthermore, the means by which the two elementsare permanently engaged is not critical. An adhesive, :1 circumferentialcrimp, a friction joint, or any other of the commonly used joining meansmay be employed.

In practice, two of the above described assemblies may be used inconjuncture, i.e., tied or taped side-by-side, in order to insuredetonation of the charge in the borehole. In this way, if one trunk linefails, completion of the blast will be achieved by the second assemblyand without the necessity of the dangerous and expensive task ofreconnecting the holes. With such duplicate assemblies the propagationof the detonation in each of the trunk lines is assured by the brisanceproduced by the explosion of the detonating fuse.

Many variations of the above described assembly are within the scope ofthis invention. For example, the sleeve may be provided with a secondshell containing an explosive charge at the end of smaller diameter,the:

second shell also being abutted against the detonatingv With such anassembly detonationv fuse branch line. from either end of the trunk lineis practicable. In complicated and interconnected blasting designs,detonation of the trunkline from either end is often highly desirable.-

Furthermore, the cylindrical sleeve need not be of' metal as describedin the exemplified embodiment of the invention. reinforced paper, or anyother material having adequate rigidity also would be suitable.

The invention has been described in detail in the fore-- going; however,it will be apparent to those skilled in the art that many variations arepossible without departure from the scope of the invention. I intend,therefore, to be limited only by the following claims.

I claim:

1. A blasting initiation assembly for cordlike explosive devices whichcomprises a tubular metal shell closed at one end and containing acap-sensitive detonating explosive charge and a tubular sleeve having aportion of larger diameter than said shell, one end of which portion isdisposed around at least the closed end portion of said shell, and theother end portion of said sleeve being of reduced diameter and having aninside diameter essentially equal to the inside diameter of said shell,said sleeve having a pair of apertures disposed directly opposite eachother in said portion of larger diameter so that the axis of saidapertures is normal to the longitudinal axis of said sleeve, each ofsaid apertures forming an opening of at least the diameter ofconventional detonating fuse and being so located that the closed end ofsaid shell is essentially contiguous to said apertures.

2. A blasting initiation assembly according to claim 1 wherein theboundary of each of said apertures is represented by a pear-shapedconfiguration.

3. A blasting initiation assembly according to claim 1 wherein the saidtubular sleeve is a sleeve of a ductile metal.

4. A blasting initiation assembly for joining lengths of low-energyconnecting cord and for transmitting a detonation impulse from saidlow-energy connecting cord to detonating fuse which comprises a tubularmetal shell having a closed end and an open end, the closed endcontaining a cap-sensitive detonating explosive and the open end adaptedfor insertion therein of a low-energy connecting cord for transmitting adetonation impulse to said detonating explosive, a tubular sleeve havinga portion of larger diameter than said shell, the end of which portionis disposed around at least the closed end portion of said shell, andthe other. end portion of said sleevebeing of reduceddiameter and havingan inside A moldable or extrudable plastic material,

diameter essentially equal to the inside diameter of said shell topermit insertion therein of a low-energy connecting cord, said sleevehaving a pair of apertures in said portion of larger diameter locateddirectly opposite each other and having a portion of their peripheryadjacent to said closed end of said shell to permit insertion throughsaid openings, in a direction normal to the longitudinal axis of saidsleeve, of a length of detonating fuse contacting said closed end ofsaid shell.

5. A blasting initiation assembly according to claim 1 wherein saidtubular metal shell contains, in addition to 1,887,122 Dufiy Nov. 8,1932 1,991,856 Motte Feb. 19, 1935 1,991,857 Lewis Feb. 19, 19352,424,374 Taylor July 22, 1947 2,739,535 Rolland Mar. 27, 1956

